Modulation apparatus



Patented Apr. 26, 1949 MODULATION APPARATUS Royden C. Sanders, Jr., Lexington, and William R. Mercer, Belmont, Mass, assignors to Raytlieon Manufacturing Company, Newton, Mass., a corporation of Delaware Application May 24, 1947, Serial No. 750,346

7 Claims. 1

This invention relates to modulating apparatus, and more particularly to apparatus for modulating electromagnetic energy in the microwave region of the spectrum.

The invention contemplates the provision of means, for example, a wave-guide section, having a perpendicularly extending branch arm receptive of a carrier wave, for deriving from said carrier wave two constituent waves of opposite phase. Said constitutent waves are applied to means, for example, a pair of non-linear impedances which terminate the opposite ends of said wave-guide section, which are also receptive, in push-pull fashion, of a modulation wave, whereby two additional constituent waves of opposite phase are derived and combine, respectively,

with said first-named constitutent waves to produce sideband waves. Said sideband waves, together with portions of said first-named constituent waves reflected from said non-linear impedances, are fed to means, for example, a second branch arm extending perpendicularly from said wave-guide section, perpendicularly to said firstnamed branch arm, whereby said sideband waves are combined and transmitted to a load, and said reflected portions of said first-named constituent waves are combined so as to suppress the same in the direction of said load.

In the accompanying specification there shall be described, and in the annexed drawing shown, an illustrative embodiment of the modulating apparatus of the present invention. It is, however, to be clearly understood that the present In said drawing, the single figure is a schematic diagram of a modulating device assembled in accordance with the principles of the present invention.

for purposes of simplicity of illustration, the branch arm I4 recedes from the observer for a short distance from the common junction I2, then bends downwardly, and is then twisted through an angle of 90.

The opposite ends of the cross-arm terminate, respectively, in non-linear impedances, for example, rectifying crystals I5 and I6, said crystals being similarly disposed with respect to each other, and having one end of each directly connected, as at I! and I8, to said cross-arm which, in turn, is grounded, as shown. Conductors I9 and 20 are connected to the remaining terminals of said crystals and pass through insulators 2| and 22 mounted in said cross-arm, said conductors being connected to the opposite ends of a center-tapped and grounded secondary winding 23 of an input transformer 24, thereby providing a push-pull input to the crystals. The transformer 24 includes a primary winding 25.

For an understanding of the operation. of the device, assume that a carrier wave we traveling I down the branch arm I3 toward th common Referring now more in detail to the aforesaid junction I2 with its electric vector pointing, arbitrarily, to the right. As this wave reaches the junction [2, it splits into two constituent waves, one, having its electric vector pointing downwardly. traveling along the cross-arm wave guide section II toward the crystal I 5, and the other, having its electric vector pointing upwardly, traveling along said wave-guide section II toward the crystal [6.

Now, further assume that a modulation wave mm is applied to the transformer 24, and that the two constituent waves derived therefrom, by reason of the push-pull connection thereof across the crystals I5 and I8, have their electric vectors pointing in opposite directions, arbitrarily, upwardly at the crystal I5 and downwardly at the crystal I6.

Thus, there arrives at the crystal I5, two oppositely-phased constituent waves, and there arrives at the crystal I6, two, also, oppositelyphased constituent waves. As a result, the phases of the side band wciwm produced, respectively, at the crystals I5 and I6 may be considered negative inasmuch as the component waves of each are of opposite phase.

The similarly-phased sideband waves thus produced, together with the out-of-phase portions of the carrier constituent waves reflected from the crystals I5 and I6, travel. along the waveguide section II toward the common junction I2. At said junction, the sideband waves combine and are propagated along the branch arm I4, The

crystal-reflected carrier waves combine and are propagated back along the branch arm I3 from whence the initial carrier wave came, but since these crystal-reflected carrier waves are of opposite phase, they are suppressed in the direction of the branch arm l4. Thus sideband and carrier waves are effectively separated.

While the branch arm 13 has, in the foregoing description, been considered as the input for the carrier wave, it is desired to point out that the branch arm H may be used as the input for the carrier, in which case the branch arm l3 becomes the output for the sidebands.

This completes the description of the aforesaid illustrative embodiment of the present invention.

What is claimed is:

1. Modulating apparatus comprising: means, receptive of a carrier wave, for deriving therefrom two constituent waves; means, receptive of a modulation wave and receptive of said constituent waves, for deriving from the former two additional constituent waves of opposite phase, and

' combining the same, respectively, with said firstnamed constituent waves whereby sideband waves are produced; and means, receptive of said sideband waves and receptive of portions of said flrstnamed constituent waves reflected from said lastnamed means, for combining said sideband waves and transmitting the same to a load, and combining said reflected portions of said first-named constituent waves and suppressing the same in the direction of said load.

2. Modulating apparatus comprising: a waveguide section, having a perpendicularly extending branch arm receptive of a carrier wave, for deriving from said carrier wave two constituent waves; means, terminating the opposite ends of said wave-guide section, receptive of a modulation wave and receptive of said constituent waves, for deriving from the former two additional constituent waves of opposite phase, and combining the same, respectively, with said first-named constituent waves whereby sideband waves are produced; and a second branch arm extending perpendicularly from said wave-guide section, per:

pendicularly to said first-named branch arm, receptive of said sideband waves and receptive of portions of said first-named constituent waves reflected from said last-named means, for combining said sideband waves and transmitting the same to a load, and combining said reflected portions of said first-named constituent waves and suppressing the same in the direction of said load.

3. Modulating apparatus comprising: a waveguide section, having a perpendicularly extending branch arm receptive of a carrier wave, for deriving from said carrier wave two constituent waves; a pair of now-linear impedances terminating the opposite ends of said wave-guide section, receptive of a modulation wave and receptive or said constituent waves, for deriving from the former two additional constituent waves of opposite phase, and combining the same, respectively, with said first-named constituent waves whereby sidee 6 v.M/pcdances, for combining said sideband waves and transmitting the same to a load, and combining said reflected portions of said first-named con- 4 stituent waves and suppressing the same in the direction 01' said load. g

4. Modulating apparatus comprising: a waveguide section, having a perpendicularly extending 5 branch arm receptive of a carrier wave, for deriving from said carrier wave two constituent waves; a pair of non-linear impedances terminating the opposite endsof said wave-guide section, receptive, in push-pull, of a modulation wave and receptive of said constituent waves, for deriving from the former two additional constituent waves of opposite phase, and combining the same, respectively, with said first-named constituent waves whereby sideband waves are produced; and a second branch arm extending perpendicularly from said wave-guide section, perpendicularly to said first-named branch arm, receptive of said sideband waves and receptive of portions 01' said first-named constituent waves reflected from said non-linear impedances, for combining said sideband waves and transmitting the same to a load, and combining said reflected portions of said first-named constituent waves and suppressing the same in the direction or said load.

5. A balanced modulator comprising: a waveguide section having a non-linear impedance at each of its opposite ends; a carrier-receiving branch arm extending perpendicularly from said wave-guide section; a source of modulation; an

impedance, receptive of said modulation, connected in push-pull relationship to said nonlinear impedances; branch arm extending perpendicularly from said wave-guide section perpendicularly to said carrier-receiving branch arm.

6. A balanced modulator comprising: a waveguide section having a crystal detector at each of its opposite ends; a carrier-receiving branch arm extending perpendicularly from said wave-guide section; source of modulation; an impedance,

receptive of said modulation, connected in pushpull relationship to said crystal detectors; and a sideband-receiving branch arm extending perpendicularly from said wave-guide section, perpendicularly to said carrier-receiving branch ""arm. flm

7.-A balanced modulafif'comprisingz a waveguide section having anon-lihear impedance at each of its opposite ends; a carrier-receiving branch arm extending perpendicularly from said 'wave-guideflsection; a modulation-receiving impedance connected in push-pull relationship to said non-linear impedances; a sideband-receiving branch arm extending perpendicularly from said wave-guide section, perpendicularly to said carrier-receiving branch arm; and a load connected across said sideband-receiving branch arm.

ROYDEN C. SANDERS, J R. WILLIAM R. MERCER.

REFERENCES CITED ---Ilre foll9wingreferences are of record in the cnflleobthis patent:

UNITED STATES PATENTS Number Name Date 2,211,003 Conklin Aug. 13, 1940 2,257,783 Bowen Oct. 7, 1941 2,408,420 Ginzton Oct. 1, 1946 FOREIGN PATENTS Number Country' Date 116,110 Australia Nov. 4, 1942 and a sideband-receiving 

